1. Field of the Invention
The present invention relates to a slip suppression control system for a vehicle which is configured to control a wheel driving power according to a wheel traction state on a road surface.
2. Description of the Related Art
Conventionally, there is proposed a traction controller configured to reduce an engine driving power to restore a drive wheel traction on a road surface (e.g., see Japanese Laid-Open Patent Application Publication No. Hei 7-103009). This controller uses traction control for retarding an ignition timing of the engine with respect to an optimal timing to reduce the driving power if an increase rate of an engine speed exceeds a predetermined start threshold, thus inhibiting a slip.
When a slip occurs in a state where the vehicle is driving on a road surface having a low-friction resistance as a whole, the slip continues for a relatively long time. On the other hand, when the vehicle is driving through a small low-friction resistance region on the road surface, such as a gap on the road surface or a wet manhole, an instantaneous slip occurs, but the drive wheel traction on the road surface is restored immediately. In that case, if the termination of the traction control is delayed until a specified programmed termination condition is satisfied, drivability may be degraded. That is, in the situation where the drive wheel is driving through the gap on the road surface but the driver does not feel a slip, for example, it is desirable to terminate the traction control immediately.